Chapter 5 - Chapter 5 Newtonian Mechanics Ch 5 Force and...

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Chapter 5 Newtonian Mechanics
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Ch 5 Force and Motion Summery of Motion Force Newton’s 1 st Law Reference Frames Newton’s 2 nd Law Mass Free Body Diagram
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What did we learn so far? How do objects move? Position, velocity and acceleration as a function of time. Example : 1D-motion with a constant acceleration. 3-d motion with constant acceleration r r ( t ), r υ ( t ), r a ( t ) x ( t ) = x 0 + 0 t + 1 2 at 2 ( t ) = 0 + at a = costant
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Why do objects move? Historical prospective: Aristotle: The natural state of an object is to be at rest. For an object to move with a constant velocity a force needs to be applied. Galileo Galilei: He recognizes that if a moving object is not disturbed by external forces it will keep moving at a constant rate. Frictionless surface r υ = constant
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Newton’s First Law Formulation: If no force acts on a body, the body’s velocity cannot change. If no force acts on an object it remains at rest or it continues its linear uniform motion. Example:
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A few pointers A linear and uniform motion is as “natural” for a body as for it to be at rest. The presence of an acting force is not a reason by itself for an object to be moving. If a body is not moving uniformly, there is a force acting on it! If a body is moving on a curved trajectory there is definitely a force acting on it. a 0
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Force The force is a vector : Magnitude Direction Application point The force has 3 components: Unit: N (Newton) 1N is the force that results in acceleration of 1 m/s 2 when applied to a standard body with mass 1 kg . r F = F x ) i + F y ) j + F z ) k F x F y F z r F x y z r F
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Net Force: Forces add and subtract as vectors . The sum of all forces acting on a single body is called net force (resulting force). Principle of superposition : The effect of all forces acting on a single, point mass is equivalent to the effect of a single force (the net force) acting on this body. r F net r F 1 r F 2 r F net r F net = r F 1 + r F 2 + r F 3 + ...
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Newton’s First Law : an object will stay at rest , or maintain its motion at a constant velocity and in a straight line as long as no force is exerted on the object , or all forces cancel each other (F net =0) Says who? An observer at rest, or moving at a constant speed. G
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This note was uploaded on 03/12/2010 for the course PHY 2049 taught by Professor Any during the Spring '08 term at University of Florida.

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Chapter 5 - Chapter 5 Newtonian Mechanics Ch 5 Force and...

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